For scientists who study the human immune system, the penny dropped at different points in the early frenetic months of the Covid-19 pandemic. Looking back now, many marvel at the realization that they witnessed and were able to chronicle something no other scientists had ever actually seen.

The Covid pandemic marked the first time people armed with powerful scientific tools could study how the immune system awakens to and develops defenses against a new threat, in real time, in the global population. Think about it: At the start of 2020, the immune systems of nearly 8 billion people were effectively blank slates as pertains to this new coronavirus.

"I’ve never had the ability to access samples where I could track the evolution of an immune response from what we call naive cells that have never been activated before to multiple boosts that were timed, we could actually watch an immune system develop in a way that we have never been able to do before.”